From mboxrd@z Thu Jan 1 00:00:00 1970 From: hanjun.guo@linaro.org (Hanjun Guo) Date: Fri, 24 Jan 2014 23:53:34 +0800 Subject: [PATCH 18/20] clocksource / acpi: Add macro CLOCKSOURCE_ACPI_DECLARE In-Reply-To: <20140124151513.GD19052@arm.com> References: <1389961514-13562-1-git-send-email-hanjun.guo@linaro.org> <1389961514-13562-19-git-send-email-hanjun.guo@linaro.org> <20140122114537.GA15591@e106331-lin.cambridge.arm.com> <52E1B1DE.5050507@linaro.org> <20140124120815.GH814@e106331-lin.cambridge.arm.com> <20140124151513.GD19052@arm.com> Message-ID: <52E28C7E.5070509@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2014?01?24? 23:15, Catalin Marinas wrote: > On Fri, Jan 24, 2014 at 12:08:15PM +0000, Mark Rutland wrote: >> On Fri, Jan 24, 2014 at 12:20:46AM +0000, Hanjun Guo wrote: >>> On 2014?01?22? 19:45, Mark Rutland wrote: >>>> On Wed, Jan 22, 2014 at 08:26:50AM +0000, Linus Walleij wrote: >>>>> On Fri, Jan 17, 2014 at 1:25 PM, Hanjun Guo wrote: >>>>> >>>>>> From: Amit Daniel Kachhap >>>>>> >>>>>> This macro does the same job as CLOCKSOURCE_OF_DECLARE. The device >>>>>> name from the ACPI timer table is matched with all the registered >>>>>> timer controllers and matching initialisation routine is invoked. >>>>>> >>>>>> Signed-off-by: Amit Daniel Kachhap >>>>>> Signed-off-by: Hanjun Guo >>>>> Actually I have a fat patch renaming CLOCKSOURCE_OF_DECLARE() >>>>> to TIMER_OF_DECLARE() and I think this macro, if needed, should >>>>> be named TIMER_ACPI_DECLARE(). >>>>> >>>>> The reason is that "clocksource" is a Linux-internal name and this >>>>> macro pertains to the hardware name in respective system >>>>> description type. >>>>> >>>>>> +#ifdef CONFIG_ACPI >>>>>> +#define CLOCKSOURCE_ACPI_DECLARE(name, compat, fn) \ >>>>>> + static const struct acpi_device_id __clksrc_acpi_table_##name \ >>>>>> + __used __section(__clksrc_acpi_table) \ >>>>>> + = { .id = compat, \ >>>>>> + .driver_data = (kernel_ulong_t)fn } >>>>>> +#else >>>>>> +#define CLOCKSOURCE_ACPI_DECLARE(name, compat, fn) >>>>>> +#endif >>>>> This hammers down the world to compile one binary for ACPI >>>>> and one binary for device tree. Maybe that's fine, I don't know. >>>> How does it do that? >>>> >>>> As far as I could tell CONFIG_ACPI and CONFIG_OF are not mutually >>>> exclusive, and this just means that we only build the datastructures for >>>> matching from ACPI when CONFIG_ACPI is enabled. >>>> >>>> Have I missed something? >>>> >>>> I definitely don't want to see mutually exclusive ACPI and DT support. >>> ACPI and DT did the same job so I think they should mutually exclusive. >>> if we enable both DT and ACPI in one system, this will leading confusions. >> ACPI and DT do similar jobs, and we should be mutually exclusive at >> runtime. However, they should not be mutually exclusive at compile-time. >> >> Being mutually exclusive at compile-time is just broken. It creates more >> work for distributions (who need to ship double the number of kernels), >> it increases the number of configurations requiring testing, and it >> makes it easier for bugs to be introduced. It's just painful, and >> there's no reason for it. > I fully agree (IOW, I'll NAK patches that break this assumption; we want > single kernel image whether it uses DT or ACPI). I will not break this in next version, because I totally agree with Mark too :) > >> At boot time the kernel needs to decide which to use for hardware >> description, and completely ignore the other (which should not be >> present, but lets not assume that or inevitably someone will break that >> assumption for a quick hack). >> >> The same kernel should boot on a system that has a DTB or a system that >> has ACPI tables. On a system that's provided both it should use one or >> the other, but not both. > Do we still need the chosen node to be passed via DT for command line, > even if the kernel uses ACPI? It depends, but I would prefer not. I prefer UEFI+ACPI and then we don't need the chosen node to be passed via DT. Thanks Hanjun